Some writers prefer to call this fallacy “the modal scope fallacy” by which they mean that the fallacy consists of constricting the ‘scope’ of the necessity from the entire conditional (wide scope) to just its consequent (narrow scope).

Which is what you did:

Antecedent ¦ Consequent——————————————————¦————————————————-
If it is true that I am married ¦ I cannot be a bachelor.

“Two admirals, A and B, are preparing their navies for a sea battle tomorrow. The battle will be fought until one side is victorious. But the ‘laws’ of the excluded middle (no third truth-value) and of noncontradiction (not both truth-values), mandate that one of the propositions, ‘A wins’ and ‘B wins’, is true (always has been and ever will be) and the other is false (always has been and ever will be). Suppose ‘A wins’ is today true. Then whatever A does (or fails to do) today will make no difference; similarly, whatever B does (or fails to do) today will make no difference: the outcome is already settled. Or again, suppose ‘A wins’ is today false. Then no matter what A does today (or fails to do), it will make no difference; similarly, no matter what B does (or fails to do), it will make no difference: the outcome is already settled. Thus, if propositions bear their truth-values timelessly (or unchangingly and eternally), then planning, or as Aristotle put it ‘taking care’, is illusory in its efficacy. The future will be what it will be, irrespective of our planning, intentions, etc.”

If Paul has one daughter and two sons, then Paul has to have at least one son.
Paul has one daughter and two sons.
Paul has to have at least one son.

This is wrong indeed.

It’s wrong but it is a valid argument so the first premise is false.

There is nothing wrong with the premise. But the first sentence is expresses a logical necessity, and the conclusion can be interpreted as physical necessity. And that is the fallacy. You obviously did not read the rest of my posting.

And it’s you who has problems with the logic. My only problem here is that I sometimes are not very precise in my expressions, and then you duck on it like a falcon on a mouse, missing everything I mean.

The solution offered is that there is something wrong with the premise

As there is no equivocation between has to in the first premise and has to in the conclusion, your solution doesn’t work.

No. Schwartz (above I gave my explanation), is that the scope of the modal operator is shifting:

1. It is necessary that (if Paul has one daughter and two sons, then Paul has at least one son)

To:

2. If Paul has one daughter and two sons, then Paul necessarily (has at least one son).

Schwartz points out that 1 is the exact formulation, but we often write it as 2. But correctly interpreted, as most people do, Stephen, there is no problem at all, and nobody will conclude that Paul necessarily has a son. I guarantee you in every possible world were somebody has 2 sons, he at least has one son.

The problem as originally posited is meaningless as it mixes fact with speculation.

No, speculation has nothing to do with it.

You must be one or the other is not speculation.

When I say if it is the case that you are married that is not speculation, I just point out the logical consequences.

Stephen

But we have already established that “I am married” is true, therefore “I could have been a bachelor” is speculation. I could have been a goat or an ant, but what has that to do with the factual condition of being married now?

StephenLawrence - 12 May 2011 01:44 AM
It’s a necessary condition of having free will that certain truths about the future could be false.

and

So the truth that you are married could be false, since you can’t be both married and a bachelor

That was my point.

(premise a) It is true that you are married (now)
(premise b)It can be true that you are a bachelor (in the future)

(conclusion)Which is the same as saying it can be false that you are married.

No, it is not the same.
By your own words, “you can’t be both married and a bachelor”. However I could be a bachelor in the future IF I decided to divorce my wife. But this introduces a new condition which changes the “current” true condition of “I am married” to a new true condition (a) where “I am no longer married”.
But that does not change (a) from being true now, only that (b) was true in the past and can be true in the future, but neither renders current (a) false.

Antecedent ¦ Consequent---------------------------------¦---------------------------------If it is true that I am married ¦ I cannot be a bachelor.---------------------------------¦---------------------------------

You are missing the most basic facts of logic.

It’s a basic fact of logic that this is incorrect, yes?

No, of course not.

If I have 2 sons, I cannot have no son.
If I am married, I cannot be a bachelor.

Both are true as it can be, per definition, logically.

Try Schwartz’ method:
1. If I am married, I cannot be a bachelor.

Rewrite:
2. If I am married then I am necessarily not a bachelor.

Clearer formulation:
3. It is necessary that (if I am married then I am not a bachelor).

And then you, and you alone, choose the literary interpretation of 1, and conclude, with the fact that I am married, that I am saying:

Antecedent ¦ Consequent---------------------------------¦---------------------------------If it is true that I am married ¦ I cannot be a bachelor.---------------------------------¦---------------------------------

You are missing the most basic facts of logic.

It’s a basic fact of logic that this is incorrect, yes?

No, of course not.

If I have 2 sons, I cannot have no son.
If I am married, I cannot be a bachelor.

Both are true as it can be, per definition, logically.

Try Schwartz’ method:
1. If I am married, I cannot be a bachelor.

Rewrite:
2. If I am married then I am necessarily not a bachelor.

Clearer formulation:
3. It is necessary that (if I am married then I am not a bachelor).

And then you, and you alone, choose the literary interpretation of 1, and conclude, with the fact that I am married, that I am saying:

4. I am necessarily married.

You put the modal fallacy in my mouth.

Ok, your first answer was to do with equivocation between logical necessity I think the right term might have been relative necessity and physical necessity, which had nothing to do with it. You also brought up confusing reality with language which had nothing to do with it.

You finally brought up my taking a literal interpretation of 1, which I do accept as an answer, although when you draw a diagram and say this is basic logical truth it’s hardly surprising that I take it literally.

Anyhow I tentatively accept the modal scope fallacy isn’t a problem as I had thought.